Entity Relationship (ER) Modeling - Alex Kuhl

Entity Relationship (ER) Modeling

ERDs

A diagram of the end-user view of a DB Primary goal is to model

Attributes Relationships Entities (duh)

They look like this!

The Types

Chen

Emphasis on modeling

Crow's Foot UML

Both of these focus more on design and implementation

In reality you can implement your DB from either

Review

Entities corresponds real-world objects

Entity and object are used interchangeably Entity Set collection of entities Entity Instance or Occurrence a particular entity,

basically a row in a table Represented by a named rectangle in ERDs

Attributes entity characteristics

Connected ovals in Chen and listed in the rectangle in Crow's

Can be required or optional (but optional can be bad if implemented wrong!)

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